To begin to understand the biology of aging, we propose to identify genes which are differentially expressed during aging, and determine the mechanisms for this regulation. The heat shock protein 70 (hsp7O) gene was found to be induced in muscle during aging, and using transgenic flies, this induction was found to require previously unidentified promoter elements. These same novel elements may also mediate hsp7O induction by oxygen radicals. We propose to analyze in detail the promoter sequences and trans-acting factors which regulate aging-specific hsp7O expression, and their possible relationship to oxygen radical production. To identify additional genes with aging-specific expression patterns, we have analyzed 600 fly lines containing genetically engineered transposons called "enhancer-traps", which act as reporters for the expression patterns of genes. 12 lines exhibit various aging- and tissue-specific expression patterns. The genes identified by several of these enhancer- traps will be identified, cloned and analyzed, with the goal of understanding the mechanisms for tissue-specific changes in gene expression during aging.